Surgical implantation of biological tissue is well known, and has many clinical applications. The source of the tissue may be the patient himself (autologous tissue), a member of the same species as the patient (homologous tissue), or a member of a different species (heterologous tissue). Examples of tissues which have been implanted as bioprosthetic materials are tendons, ligaments, heart valves, bone, skin patches, collagen, pericardial tissue patches, arteries, and many others. The introduction of methods for rendering tissues non-antigenic has made it possible to transplant tissue derived from various animal species into humans to repair or replace defective body parts.
The preparation of biological tissue for implantation frequently includes treatment with a chemical agent that "fixes" (i.e., "tans") the tissue. Various aldehydes have been used for this purpose, including glyoxal, formaldehyde, dialdehyde starch, and glutaraldehyde. Glutaraldehyde is considered by many to be the preferred tanning agent, and is also used as a tissue sterilant, having proven to be a good barrier against microbial contamination. Glutaraldehyde treatment is also known to render tissue substantially non-antigenic so that transplanted heterologous tissue does not elicit an adverse immune response in the recipient. Aldehyde-treated tissue is commonly rinsed with sterile distilled water or a solution such as saline prior to surgical implantation, in an attempt to remove residual aldehyde compounds from the tissue. Certain post-implantation problems, such as inflammation and other adverse reactions in some patients, are believed in some cases to be caused by residual aldehyde in implanted bioprosthetic tissue.